This invention is related to a hand tool for applying hot melt adhesive and, in particular, to such a tool which has its applicator roller positioned above the liquid level of the adhesive in the rest position of the tool so that leakage of the adhesive around the applicator roller due to gravity is prevented.
Hot melt adhesives are in popular use for conveniently attaching various items to each other. One example of such use occurs in the field of publishing in which a page layout of text and/or graphics is composed from many separate items carrying different pieces of information which are to be combined on a single page. In designing the layout of the page, small papers which carry portions of the layout are glued to a work surface. For purposes of the following discussion, the term "workpieces" designates the various pieces of paper which are to be attached to the work surface which, for example, can be a cardboard sheet. In some usages, the adhesive properties of the "glue" are sought to be as weak as possible so that the workpieces can be easily lifted without damage and placed somewhere else. A term of art for this type of adhesive might be a "wax". All the various types of adhesives are generally referred to herein by the term "hot melt adhesive".
In order to affix the workpieces to the work surface, each workpiece is first turned over so that its back is exposed, and an adhesive is then applied to it. The workpiece is then turned over again so that the text on it is visible. The workpiece is then placed on the work surface at the desired position. After the workpiece is placed on the work surface, a brayer cylinder is forcefully rolled ove the workpiece to firmly press it against the work surface in order to evenly distribute the adhesive and flatten out the workpiece.
One hot melt adhesive tool in common use is constructed of a housing with a handle extending horizontally backward therefrom. An applicator roller is rotatably attached to the bottom of the housing opposite a slot. The slot communicates a chamber in the housing with the roller. A heater is mounted inside the chamber which is large enough to accommodate several tablets or bars of solid adhesive which are melted by the heater when it is connected to a power source. A gasket between the housing and roller is provided in an effort to prevent leakage of the adhesive from the chamber, down along the applicator roller, and onto a rest surface when the tool is not in use. Leakage of the adhesive is likely because it is continuously kept in a liquid state by the heater carried inside the chamber, and the liquid lies directly atop the slot. It is desirable to keep the adhesive liquefied in order to enable instant use of the tool when required. Otherwise, time would have to be wasted in waiting for the adhesive to melt if the heater were only plugged in when its use was immediately required. However, although the above-mentioned gasket is provided to prevent such leakage, it functions unsatisfactorily. A tight seal between the applicator roller and gasket cannot be provided because it would require substantial pressure applied between the applicator roller and the gasket. Such pressure would, of course, hinder the free rolling action of the applicator. Therefore, although some pressure is applied between the roller and the gasket, it is not adequate to act as a liquid-tight seal. Also, with use and aging, the gasket tends to wear and/or shrink a bit, and this forms an additional route by which the adhesive can leak onto the rest surface. Thus, the fact that the applicator roller is in the direct path of the hot melt adhesive which is continuously attracted downward by gravity causes an inevitable leakage of adhesive and the resultant messiness, as well as the waste of adhesive.
A further disadvantage of the hand tools in current use is the requirement to use a separate tool as the brayer roller. Labor time is wasted in manually switching between the adhesive applicator and the brayer while affixing the workpieces to the work surface.